A ROPS for a work vehicle according to U.S. Pat. No. 5,503,430 includes a pair of left and right lower posts extending in a curve from vicinity of a transmission and a portal-shaped upper crossbar. Base end portions of the lower posts are fixed to a vehicle body. Left and right lower end portions of the upper crossbar are pivotally connected to upper end portions of the respective lower posts to be pivotable about a horizontal axis and connected and fastened thereto with connecting bolts. At connecting portions of the lower post and the upper crossbar, there are provided an engaging portion and an engaged portion which are opposed to and engaged with each other. Under a free state releasing the bolt fastening between the lower post and the upper crossbar, the engaging portion and the engaged portion are resiliently separated from each other in an engagement releasing direction. With this, the upper crossbar is rendered freely pivotable. By being fixed to a desired position by the bolt fastening, the height of the ROPS is adjusted.
With the above-described ROPS, as the lower posts are long rods having complicated curved shape, the ROPS requires not only high production cost, but also high rigidness and attaching strength. Moreover, even when the ROPS is adjusted to the lowest possible height position, the height of the lower posts fixed to the vehicle body remains the same and the positions of the pivotal connection between the lower posts and the upper crossbar remain higher than the driver's seat. For this reason, with whatever adjustment of the positon of the ROPS, the lower posts will present obstacle in driver's getting on/off the vehicle and maintenance work.
A ROPS for a work vehicle according to U.S. Pat. No. 7,971,904 includes a pair of left and right leg portions, a portal-shaped crossbar and a pivotal bracket for pivotally connecting lower ends of a crossbar to upper ends of the lower leg portions. The lower leg portions have their lower ends fixed to a vehicle body frame and extend in a curve from the horizontal to an upper side, thus striding over an engine therebetween. With this ROPS too, adjustment of the ROPS to the lowest possible height does not change the height of the lower legs fixed to the vehicle body frame and this height remains lower than the driver's seat, but still higher than the engine. For this reason, with whatever posture adjustment of the ROPS, the ROPS will still present obstacle in maintenance work to be done in the vicinity of the engine.